Call Forwarding, a popular custom calling or special service in telephone networks, has been offered in Stored Program Control (SPC) switching systems for many years. To activate this Call Forwarding service, subscribers have been instructed to dial an activation code followed by a local or toll telephone or directory number (DN). Thereafter, until the subscriber dials a de-activation code, the switching system forwards all of the subscriber's calls to the thus entered forwarding directory number. In effectuating this service a party served by a local SPC switch office and who subscribes to Call Forwarding service has stored in the memory at the office, data identifying the party as a subscriber. In addition data is also stored at the office indicating if the service is activated and, if so, a directory number to which incoming calls are to be forwarded. When an incoming call is received the stored program of the office directs the interrogation of the memory data associated with the called station to determine if the called party subscribes to Call Forwarding service. If not, or if the service is not activated, the call is completed to the called station in ordinary fashion. However if a Call Forwarding service is active for the called party the stored program obtains the forwarding number from memory and from that point acts effectively as an originating office with respect to the new number. That is, the office may complete the call locally to the new number if it is served by the office, or it may seize an outgoing trunk to another local office or to a toll network, as the situation demands, and outpulse the new number to a distant office to complete the call. A system of this type is illustrated in FIG. 1.
Referring to FIG. 1 there is shown a conventional local telephone network wherein a Remote Memory Administration System (RMAS) or a MIZAR computer 10 is connected to program a series of varying type Stored Program Control (SPC) switches 12, 14, 16 and 18. RMAS and MIZAR are commercial designations used to refer to computers which are adapted to respond to input signals to generate so called "Recent Change" signals to Stored Program Control (SPC) switching systems to effect changes to line and trunk translations that have not been merged with the data base. As will be understood, such switches are controlled by a switch computer whereby the specific switching functions are implemented in a series of software routines which are commonly referred to as generics. The switch computers are distinct from the RMAS or MIZAR computer. The generics are developed by the switch manufacturer and loaded into the switch for subsequent use at the local switching office. Through the generics the switch is able to provide a predefined selection of enhanced services to any local customer that is connected to the switch. The SPC switch 14 is assumed to have generics which include a Call Forwarding Variable (CFV) and an Activation/Deactivation Flag (A/D) for each so subscribed loop terminating on the switch.
The RMAS 10 is connected to the SPC switches 12-18 by Recent Change Channels 13, 15, 17 and 19. The Recent Change Channel is a general purpose I/0 port used for programming switch translation variables including the CFV and A/D. A series of technician or RCMAC terminals 20, 22 and 24 are connected to access the RMAS. As will be understood, the RMAS runs on a separate mini-computer and provides service technicians or operators with formatted CRT screens at terminals 20, 22 and 24 to enter service orders. The RMAS translates the screen inputs into proper Recent Change requests and submits them to the appropriate CO switch in an orderly fashion.
In FIG. 1 the switch 14, which is a 1AESS switch, is illustrated in detail, it being understood that the other switches possess similar features. The SPC switches provide for a Call Forwarding Variable (CFV) 26 and an Activation/De-activation Flag (A/D) 28 for each subscriber loop terminating on the switch. Two such loops 30 and 32 are shown connecting stations 34 and 36 to the switch.
For any incoming call, if the primary destination directory number (DN) A/D flag is in the activated state, the switch performs a translation on the call to route it to the forwarded destination DN contained in the associated CFV data area. With standard Call Forwarding, the CFV and A/D must be programmed either from the subscriber's primary DN or manually by a technician at the RMAS. Conventional Call Forwarding provides an access code and a series of tone prompts to guide the customer through the Call Forwarding programming sequence.
An obvious limitation of this conventional service is that the Call Forwarding subscriber must physically be at the home or office telephone location in order to activate or deactivate the call forwarding feature or to change the "Forward To" number. This requires that the customer anticipate his need for Call Forwarding before leaving the residence or business and that he return any time that he desires to make a change. Often, however, the need for access to the service occurs at some remote location.
In order to overcome this limitation it has been proposed to provide a new feature which may be referred to as Remote Access to Call Forwarding (RACF). With Remote Access to Call Forwarding a subscriber could utilize any telephone equipped with DTMF signaling capability, dial a special access number, followed by a Personal Identification Number (PIN), and then dial additional codes in order to activate or deactivate the Call Forwarding feature. It will be understood that the PIN is a security mechanism to prevent accidental or malicious interference with features and/or services on other subscribers' telephone lines.
One approach to providing such service may be generally described as follows. In many stored program control switches technicians may use the Recent Change Administration Capability to activate and de-activate Call Forwarding on individual subscribers' lines. If a computer such as a personal computer is configured to emulate a technician terminal (RCMAC terminal) accessing the Remote Memory Administration System (RMAS), users of the remote service may dial into ports on the thus configured computer and enter appropriate commands to cause the computer to emulate the technician and activate or deactivate the Call Forwarding feature on the user's line. A system of this type is illustrated in FIG. 2.
Referring to FIG. 2 the same reference numerals are used as in describing the conventional or standard call forwarding illustrated in FIG. 1. In the FIG. 2 arrangement appropriate hardware in the form of a Remote Access Features Node (RAFN) 38 is interfaced between the RMAS 10 and a hunt group 40 associated with a Remote Access Directory Number (RADN) 42. With this configuration call forwarding requests can be collected from customers via the hunt group, processed in the RAFN and RMAS and issued to the CO switch 14.
With this arrangement the telephone answering service interface will detect when the customer dials the RADN and inform the RAFN or processor 38 of the event. The processor (which may contain a voice response unit) will direct appropriate voice messages to the customer to obtain the information required to perform the customer's call forwarding request. All input by the customer will be in the form of DTMF digits which will be received by the answering service interface and passed to the processor. When all required information has been collected from the customer, the processor will assemble the forwarding request and transmit it to the RMAS for execution. Additionally should a technician terminal be connected to the switching office destined for the CFV change, the RAFN must wait for completion prior to execution of the change.
However, while this architecture is capable of effecting remote access to Call Forwarding it presents a number of problems. The principal of these problems is delay. After the user dials into the computer it requires an excessive time to activate the feature because commands generated by the computer must be queued with all of the other memory administration work activity, not necessarily destined for the CFV subscriber's office, generated by technician terminals connected to the RMAS.
Another obstacle to implementation of RACF service is the presence and current use of multiple types of switches in most existing telephone networks. One example of a switch by switch approach to this problem is illustrated in U.S. Pat. No. 4,232,199 to Boatwright et al, issued Nov. 4, 1980. This patent describes a special service add-on for a central office which uses a dial pulse activated switch. The main thrust of the patent is the development of a central office add-on device which will permit special services to be offered from offices using step-by-step switching. The add-on unit which is specifically described includes Call Forwarding as well as a number of other special or enhanced services. The Call Forwarding service may be controlled by the subscriber from his own subscriber telephone or any other telephone equipped with DTMF dialing. Such remote programming is performed by dialing a directory number assigned to a remote programming port in the add-on unit to enable the subscriber to access the add-on in a remote programming mode.
Another approach to providing Remote Access to Call Forwarding which has been deployed in the U.K. is to place a Modular Services Node (MSN) between the customer's loop and the CO switch. The MSN consists of a digital switch, a voice announcement system and a controlling processor. It can service several hundred subscriber loops. With this arrangement the answering service interface of the MSN can handle the remote call from the customer with voice guidance. It can prompt the caller for his primary destination DN, his PIN, his desire to activate or de-activate and his forwarded destination DN. It would then program the CO switch by emulating his primary station. The principal weakness of this design is that hardware is dedicated to each customer loop requiring extremely large amounts of hardware to service a significant number of subscribers, which imposes a high cost. A second weakness is the need to hard wire customers desiring the change capability, thereby making the offering more labor intensive.
Yet another approach to handling varying types of switches is described in U.S. Pat. No. 4,878,240 to Lin et al, issued Oct. 31, 1989. The Lin et al patent discloses an arrangement which provides an adjunct switch unit for each involved central office switch. The Lin et al arrangement provides each subscriber with two telephone numbers. One number is the published number which is known to the central office switch and is the number that the public would dial to reach the subscriber. The other number is known only to an adjunct which is provided for the switch. Incoming calls to the subscriber's published number are routed by the central office switch (as through a call forwarding feature) to the adjunct where it is then routed through an additional programmable switch for the duration of the call. Based upon the services subscribed to by the called party and based upon the condition of his telephone line (i.e., answered, busy or not answered), the call is routed to the other adjunct known number of the called party. The adjunct then causes the ringing of the subscriber's telephone, or if call forwarding is activated, to ring the published number of the forwarding party in order to ring the telephone there. This arrangement involves a significant investment in sophisticated adjunct equipment and a basic change in the way switching is handled in a central office switching system.
Still another approach to RACF is the use of customer premise equipment (CPE). However, a CPE version requires multiple calls by the user. The first call initiates a timing sequence in the CPE which enables a follow-up call, if made within the prespecified timing sequence, to deactivate the present forwarding condition. A subsequent call will allow for remote activation of the CFV feature. An apparatus for effecting CPE type control is illustrated in U.S. Pat. No. 4,475,009 to Rais, issued Oct. 2, 1984. As with all CPE equipment the apparatus described in the Rais patent is effective for remotely controlling Call Forwarding for the particular line to which it is connected.